1. Field of the Invention
The present invention relates to a method and apparatus for packaging and, more particularly, relates to a method and apparatus for automatically wrapping each of a series of open trays filled with suitable articles in plastic film material.
2. The Prior Art
Automatic wrapping machines have found wide use for packaging articles in a thin, clear, and tough plastic film. A major use of such machines is found in retail food stores, wherein plastic or fiber trays are filled with meat or vegetable products and sealed on all sides by a thin plastic wrap. The wrap contains the contents and protects them against contamination and also facilitates handling and sale of the product. Such wrapping of produce is done at the retail site, where machines are frequently operated by relatively inexperienced personnel. This requires that the machines be simple to use and safe, as well as efficient and quick in operation.
Illustrative of the prior art is U.S. Pat. No. 3,378,990 which discloses a modern, compact semi-automatic wrapping machine. U.S. Pat. No. 3,791,101 discloses placing a film curtain across the path of advance of a package, whereby motion of the package from one support surface to the next wraps the front, bottom, and top of the package in the plastic film for subsequent formation of a lap seam on the rear of the package. U.S. Pat. No. 4,033,089 concerns a wrapping machine in which the tray advances horizontally fully at one level through the machine and a retractable tucker and undersealer device passes beneath the tray to join opposed ends of the film in a lap joint along the bottom of the tray.
Typically, plastic film shrinkage is employed to tightly seal the film about the tray. In accordance with this technique, plastic film is heated, placed about an article, and allowed to cool resulting in the film material shrinking tightly about the article. Such heat shrinking packaging machines are necessarily further complicated by the inclusion of film heating equipment.
The present invention is directed to an automatic wrapping machine adapted to resiliently stretch plastic film material about an article being packaged, thus eliminating heat shrinking mechanisms. The inventive arrangement enables articles to be passed consecutively in seriatim through the machine wrapping stations in an automatic fashion and permits consistent handling of the articles for producing sealably wrapped products, such as in a supermarket.